Dispensers of therapeutic solutions to the eye, ear canal, nose, or mouth are well known in the art. In particular, drop dispensers that dispense solutions to a certain part of the eye, in different amounts, or with associated apparatuses for various purposes have been described. In the typical design, a person desiring to put a solution into their own eye is required to tip their head back, pull one or both of their eyelids back, center the dropper over the eye and squeeze out a drop of solution. Some designs have an arm for bracing a bottle, or dispenser, on the cheek, just under the eye, while other designs have elaborate trusses for centering the bottle over the eye, while holding the eyelids back. However, despite the plethora of options available, many dispensers still require the person to assume an uncomfortable position not conducive to using a mirror to aid in the administration, or in the process of administering a solution, they either blink or miss the eye completely, spilling the solution or requiring additional applications. This can be a wasteful process, especially considering the fact that many therapeutic solutions for the eye or ear tend to be quite expensive and may have to be refilled by a pharmacist.
Improper administration of a therapeutic solution by a patient may also account for waste of sometimes expensive ophthalmic pharmaceutical agents, despite explicit administration instructions from a clinician or provider. One such example is eye drops to treat glaucoma. Some glaucoma treatments require patients to administer medicated eye drops, which lower the eye pressure to prevent optic nerve damage and loss of vision. Yet, despite instruction on proper eye drop dispensation and placement, more than one-half of glaucoma patients incorrectly administer drop medication. One factor of improper administration is the dispensing of too little or too much drug per indicated single drop.
Too much or too little drug per drop from a drop dispenser can be caused by the angle of administration. For example, a 45° angle of administration of a drop from a traditional drop dispenser delivers a drop of a different volume than that compared to the same dispenser when held at a 90° angle to the eye. Such differences have been determined using densitometry methods. These methods determine the amount of solution dispensed from a drop dispenser by mass determination and conversion to drop volume based on density. Such drop size differences have been assessed for a wide range of products such as prostanoid analogues Xalatan®, Lumigan® and Travatan® with a once-daily recommended dosage. Difference in drop size between 45° and 90° administration angles were statistically significant for both Travatan and Lumigan (Mann-Whitney, p<0.001), however Travatan demonstrated a substantial higher level of discrepancy. The amount of drug delivered by a Travatan bottle increases approximately 16% when administered at a 90° angle vs. a 45° angle to the eye. Such variation in the angle of administration of topical ophthalmic therapy for conditions such as glaucoma can have a significant effect not only in the amount of drug delivered to the eye, but in regard to the costs of medication as well. Gaynes, B. I. and Singa, R. M., unpublished results and also Gaynes, B. I.; Singa, R. M., Schaab, G., and Sorokin, Y., J. Ocular Pharmacology and Therapeutics 23(2), 196-201 (2007). Other drop size determinants have been addressed by Santvliet, L. V. et al. Survey of Ophthamology 49, 197-213 (2004).
Variation in drop size can also have an impact on overall effectiveness of the drug. For example, too small of a drop to the eye will not result in the desired treatment, however if too large a drop is dispensed the eye cannot absorb all of the drug and excess drug will be expelled during the blinking process or excess tear formation will dilute the drug. Any one of these results can affect the treatment outcome and may lead to wasteful use of sometimes expensive pharmaceutical solutions.
A need exists for drop dispensers that are easy to use and allow a person to self-apply a drop of a therapeutic solution to their own eye in a comfortable manner and in a correct dosage amount.